The spectral radius of connected non-regular graphs is considered. Let λ1 be the largest eigenvalue of the adjacency matrix of a graph G on n vertices with maximum degree ∆. By studying the λ1-extremal graphs, it is proved that if G is non-regular and connected, then ∆− λ1 > ∆+ 1 n(3n+∆− 8) . This improves the recent results by B.L. Liu et al. AMS subject classifications. 05C50, 15A48.

Stanford University Let x 1 denote the square of the largest singular value of an n × p matrix X, all of whose entries are independent standard Gaussian variates. Equivalently, x 1 is the largest principal component variance of the covariance matrix X′X, or the largest eigenvalue of a p-variate Wishart distribution on n degrees of freedom with identity covariance. Consider the limit of large p ...

In this paper we propose an iterative method for calculating the largest eigenvalue of an irreducible nonnegative tensor. This method is an extension of a method of Collatz (1942) for calculating the spectral radius of an irreducible nonnegative matrix. Numerical results show that our proposed method is promising. We also apply the method to studying higher-order Markov chains.

Let G = (V, E) be simple graphs, as graphs which have no loops or parallel edges such that V is a finite set of vertices and E is a set of edges. A weighted graph is a graph each edge of which has been assigned to a square matrix called the weight of the edge. All the weightmatrices are assumed to be of same order and to be positive matrix. In this paper, by “weighted graph” we mean “a weighted...

Let G be a mixed graph. We discuss the relation between the second largest eigenvalue λ2(G) and the second largest degree d2(G), and present a sufficient condition for λ2(G) ≥ d2(G).

Cognitive radio (CR) is a promising technique for future wireless communication systems. In CR networks, dynamic spectrum access (DSA) of frequency is implemented to mitigate spectrum scarcity. Specifically, a secondary (unlicensed) user may be allowed to access the temporarily unused frequency bands granted to a primary (licensed) user. DSA has to be implemented so that the quality of service ...

Abstract. Let G be a simple undirected connected graph on n vertices. Suppose that the vertices of G are labelled 1,2, . . . ,n. Let di be the degree of the vertex i. The Randić matrix of G , denoted by R, is the n× n matrix whose (i, j)−entry is 1 √ did j if the vertices i and j are adjacent and 0 otherwise. The normalized Laplacian matrix of G is L = I−R, where I is the n× n identity matrix. ...

We study the spectral radius of connected non-regular graphs. Let λ1(n,Δ) be the maximum spectral radius among all connected non-regular graphs with n vertices and maximum degree Δ. We prove that Δ− λ1(n,Δ)=Θ(Δ/n). This improves two recent results by Stevanović and Zhang, respectively. © 2007 Elsevier Inc. All rights reserved.

Article history: Received 13 June 2008 Accepted 13 November 2008 Available online xxxx Submitted by R.A. Brualdi AMS classification: 05C50

The power method for computing the dominant eigenvector of a positive definite matrix will converge slowly when the dominant eigenvalue is poorly separated from the next largest eigenvalue. In this note it is shown that in spite of this slow convergence, the Rayleigh quotient will often give a good approximation to the dominant eigenvalue after a very few iterations-even when the order of the m...